Astragaloside IV improved insulin resistance in L6 myotubes induced by high glucose and insulin

The purpose of the present study was to examine the effects of astragaloside IV, a saponin isolated from Astragalus membranaceus (Fisch) Bge, on insulin resistance in L6 myotubes induced by high glucose and insulin (high Glc/Ins). Chronic treatment of high Glc/Ins resulted in impaired insulin-stimulated glucose transport in differentiated L6 myotubes, which was paralleled by reduced tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase activity and Akt phosphorylation. Pretreatment of insulin-resistant cells with astragaloside IV exhibited increases of insulin-mediated glucose transporter 4 (GLUT4) translocation to the plasma membrane and glucose uptake. This potentiation correlated positively with the enhancement of insulin signaling pathway by increasing tyrosine-phosphorylated IRS-1, PI 3-kinase activity and Akt phosphorylation at Thr . The results indicate that astragaloside IV may improve insulin resistance in L6 myotubes through IRS-l/PI 3-kinase/Akt signaling pathway.